In a semiconductor device manufacturing process in which a laminated structure of an integrated circuit pattern is formed on a surface of a substrate such as, for example, a semiconductor wafer (hereinafter, referred to as a “wafer”), a liquid processing is performed using a rinse liquid such as a chemical liquid to remove fine dusts or a natural oxide film. After the liquid processing, the liquid attached to the wafer is removed. In order to prevent the pattern from collapsing due to the influence of surface tension when the liquid in the pattern is dried, a technique known in the related art removes the liquid using a high-pressure fluid such as a supercritical fluid.
The supercritical fluid has small viscosity, as compared with liquid, as well as high ability to dissolve liquid. In addition, no interface exists between the supercritical liquid and gas in an equilibrium state. Accordingly, when a wafer having liquid attached thereto is placed in a supercritical fluid atmosphere, the liquid in the pattern may be replaced with the supercritical fluid substantially without applying force to the pattern. Then, the supercritical fluid is converted into gas by decreasing the pressure. As a result, the liquid may be removed while suppressing the pattern from being collapsed.
The processing of the wafer using the supercritical fluid is performed in a high-pressure chamber (e.g., a high-pressure container), and carrying-in/out of the wafer is performed through a carrying-in/out port that is configured to be opened/closed, for example, by a cover. In a high-pressure container having a high pressure atmosphere therein, it is desirable that the number of joints is as small as possible. Further, from the viewpoint of reducing the volume of the internal processing space or the force applied to the cover, the high-pressure container should be machined in such a manner that the internal processing space has a relatively small volume and/or the carrying-in/out port has a small opening area. Therefore, the present inventors have studied manufacturing a high-pressure container provided with a processing space configured to accommodate a wafer by cutting the inside of a metal block from a flank side of the block of metal.
Meanwhile, a high-pressure fluid such as a supercritical fluid has high extraction capability, and thus, elutes contaminants attached to the internal wall surface of the high-pressure container when the block is machined. Accordingly, the wafer may be contaminated.
Japanese Patent Laid-Open No. 2006-130418 discloses a technique of forming an oxide film (a passivation film) on a surface to be contacted with a supercritical fluid, for example, by electropolishing in order to suppress metal from being eluted from a high-pressure container (see, e.g., claim 1, lines 1 to 9 of paragraph 0051, lines 2 to 5 of paragraph 0058, and FIG. 4). However, the electropolishing is a finishing processing for planarizing micrometer-level unevenness and thus difficult to remove a layer of contaminants having, for example, a sub-millimeter thickness. Further, when the contaminants attached during the processing do not form an oxide film by the electropolishing, the effect of suppressing the elution to the high-pressure fluid is small.
In addition, in Japanese Patent Laid-Open No. 2008-515235, for a high-pressure processing container in which a processing of removing a resist remained on a surface of a wafer after etching is performed using a supercritical fluid, there is disclosed a technique of coating a plastic or a polymer on an inside member of the high-pressure container which comes in contact with a supercritical fluid (see, e.g., lines 1 to 3 of paragraph 0005, lines 1 to 3 of paragraph 0028, lines 1 to 2 of paragraph 0045, and FIG. 1). However, from the viewpoint of reducing the amount of the supercritical fluid used, it is desirable that the volume of the high-pressure container is as small as possible. Therefore, in some cases, the processing space is constituted as a narrow space the height of which is several millimeters to a dozen or so millimeters. In such a case, for example, if the coating inside the high-pressure container is peeled off, recoating is difficult or takes a time, thereby deteriorating maintainability.